1. Field of the Invention
The present invention generally relates to a damper disk assembly. More specifically, the present invention relates to a damper disk assembly for absorbing and attenuating torsional vibrations while transmitting torque.
2. Background Information
A clutch disk assembly used on a vehicle has a clutch function and damper function. The clutch function is provided to facilitate connecting to and disconnecting from a flywheel. The damper function is provided to facilitate absorbing and attenuating torsional vibrations transmitted from the flywheel. Generally speaking, vibrations on a vehicle include idling noises (rattling), driving noises (acceleration/deceleration rattling, droning), and tip-in/tip-out or low frequency vibrations. Part of the damper function of the clutch disk assembly is provided to prevent these noises and vibrations.
The idling noises relate to a rattling sound generated in the transmission that typically occurs when a driver shifts into neutral while waiting for the traffic signal to turn green, and releases the clutch pedal. The reason for this noise is due to a large torque fluctuation that occurs when the engine combusts as the engine torque remains low at the engine idling speed. At such a moment, the input gear and the counter gear in the transmission are subject to a tooth beating phenomenon.
Tip-in/tip-out or low frequency vibrations are due to a large body sway that occurs when the acceleration pedal is abruptly engaged and then released. When the rigidity of the drivetrain is low, a torque, which is transmitted to the tires, is fed backward from a tire side to the torque, and a backlash phenomenon results causing an excessive torque on the tires, which then results in a large transient forward/backward vibration of the body.
Concerning the idling noise, critical torsional characteristics of the clutch disk assembly are in the zero torque neighborhoods. The torque therein should be as low as possible. On the other hand, it is necessary to make the torsional characteristics of the clutch disk assembly as rigid as possible in order to suppress the forward/backward vibration in the tip-in/tip-out phenomenon. In order to solve problems mentioned above, clutch disk assemblies with two stage characteristics having two kinds of spring members have been provided. In such a design, the torsional rigidity and the hysteresis torque in the first stage of the torsional characteristics (low torsional angle region) are kept low in order to achieve a noise suppression effect when idling. Since the torsional rigidity and the hysteresis torque are set high in the second stage of the torsional characteristics (high torsional angle region), the forward/backward vibration in tip-in/tip-out phenomenon can be sufficiently attenuated. Furthermore, a damper mechanism is also known which effectively absorbs minute torsional vibration in the second stage of the torsional characteristics by means of preventing the second stage large friction mechanism from operating when minute torsional vibrations resulting from fluctuations of engine combustion are supplied.
In general, it is desirable to have different rigidities on the positive side (acceleration side) and the negative side (deceleration side) of the torsional characteristics. More specifically, it is preferable to have a relatively high rigidity on the positive side and a relatively low rigidity on the negative side. This is because that with such characteristics it is possible to suppress the fluctuation of the rotating speed when passing through the resonance point on the positive side of the torsional characteristics. Furthermore, it is also possible to achieve a good attenuation ratio for the entire range on the negative side of the torsional characteristics. As a suitable mechanism for achieving such characteristics, a damper mechanism has been known, in which the number of elastic members to be compressed on the positive side is structured to be less than the number of elastic members to be compressed on the negative side. Separate from that, another damper mechanism is known, which uses different kinds of elastic members to be compressed on the positive side and the negative side, and in which the rigidity of the elastic members compressed on the negative side is structured to be lower than that of the elastic members compressed on the positive side. In the latter case, a gap in the rotational direction is secured on one rotational direction side of the elastic member, which is compressed on the positive side. The gap is secured between the elastic member and the supporting member in order to prevent the elastic member from being compressed on the negative rotational side.
As mentioned above, the damper mechanism having different rigidities on the positive and negative sides in terms of the torsional characteristics matching the engine vibration characteristics is equipped with a plurality of elastic members arranged side by side in the rotational direction. These elastic members are installed in window parts of each circular disk member. A torsion angle stopper that restricts the relative rotation of the rotating members has pin members that affix a pair of circular disk members and protrusions provided on the outer periphery of a circular member placed between the pair of circular disk members. Each pin member is placed within a notched area formed between each protrusion and is movable in the rotational direction.
As each torsional stopper is located in the rotational direction between the elastic members, the length of the notched area is limited and it is difficult to provide a sufficient torsional angle, which in turn makes it difficult to broaden the damper torsional angle.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved damper disk assembly that absorbs and attenuates torsional vibrations while transmitting torque. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.